These investigations are designed to explore the effect of replacement of complement in the form of fresh-frozen AB/Rh- plasma on serum complement levels and opsonin activity in children with protein-energy malnutrition. Deficiency of complement and complement-mediated opsonins, known to occur in malnourished hosts, may play a role in the high prevalence of fatal gram negative septicemia in acute malnutrition. Phase I of this study will determine the natural course of complement levels and activity during optimal nutritional rehabilitation. In Phase II, complement-containing fresh-frozen plasma or complement-depleted plasma protein fractions (Plasmanate) will be administered on admission, and their effect on circulating complement levels and opsonic activity will be determined. Two additional groups will receive opsonically-active gamma globulin or albumin by the intramuscular route, and will be similarly studied. Phase III will be an open ward study of the effect of the treatment protocols on morbidity and mortality of hospitalized children with malnutrition. These studies have relevance to populations of undernourished children in developing countries as well as chronically ill adults in developed countries who also suffer from endogenous or iatrogenic protein-energy deprivation.